Beginning on Monday December 30, 2013, the Internet has been flooded with conjecture claiming that Fukushima Daiichi Unit 3 is ready to explode. Fairewinds Energy Education has been inundated with questions about the very visible steam emanating from Fukushima Daiichi Unit 3. Our research, and discussions with other scientists, confirms that what we are seeing is a phenomenon that has been occurring at the Daiichi site since the March 2011 accident.

It is winter and it is cold through out much of the northern hemisphere. Hot water vapor has been released daily by each of the four Fukushima Daiichi nuclear power plants since the accident. We believe that is one of the reasons TEPCO placed covers over Daiichi 4 and 1. Sometimes the steam [hot water vapor] is visible and sometimes it is not. If you have been outside on a cold winter day, you have personally experienced that phenomenon when you see the breath you exhale form a cloud in the cold air. The technical explanation is that hot water vapor becomes visible when it comes in contact with cold air and condenses. During the winter months in the Fukushima Prefecture, the sea air is cold and moist, thus forming the ideal conditions to see the released steam.

Why is there still steam coming from the plants especially since TEPCO says that they are in cold shutdown? As we at Fairewinds have discussed in our many videos, podcasts, and reports, radioactive rubble (fission products) was left in each unit following the triple meltdowns. While the plants are shutdown in nuke speak, there is no method of achieving cold shut down in any nuclear reactor. While the reactor can stop generating the actual nuclear chain reaction, the atoms left over from the original nuclear chain reaction continue to give off heat that is called the decay of the radioactive rubble (fission products). The heat from this ongoing decay of radioactive rubble is constantly releasing moisture (steam) and radioactive products into the environment. The radioactive decay is gradually slowing down, as fission products decay away. The cold moist winter air at this time of year is making steam from the ongoing decay easily visible.

How much radiation is escaping? When Unit 3 was operating, it was producing more than 2,000 megawatts of heat from the nuclear fission process (chain reaction in the reactor). Immediately after the earthquake and tsunami, it shut down and the chain reaction stopped, but Unit 3 was still producing about 160 megawatts of decay heat. Now, 30 months later, it is still producing slightly less than 1 megawatt (one million watts) of decay heat.

What does that figure mean; is it an inconsequential amount? 1 megawatt of decay heat is a lot of heat even today, and it is creating radioactive steam, but it is not a new phenomenon. These hot radioactive releases [not physically hot, but radioactive hot – meaning they contain radioactive fission products] have occurring for the entire 33 months following the triple meltdown. The difference now is that the only time we visibly notice these ongoing releases is on the cold days with atmospheric conditions cold enough to condense hot vapor into steam.